Timer for internal combustion hammers



Oct. 1, 1940. c. CHARLES 2,215,641

TIMER FOR INTERNAL COMBUSTION HAMMERS Filed Jan. 11, 1940 2 Sheets-Sheet 1 J7z'c e77757": Cari l. Czar/e 6,

Oct. 1, 1940. c. 1.. CHARLES TIMER FOR INTERNAL COMBUSTION HAMMERS 2 Sheets-Sheet 2 Filed Jan. 11, 1940 m W 0 6, J mw mw ii J 0,7 //v 0% m i|l .1 an W GM 6 KTW u J v Nb NW hh w kn Q Patented Oct. 1, 1940 UNITED: STATES PATENT OFFICE CarlL. Charles, Winnetka, 111., assignor to Gas Tool Patents Corporation, a corporation of Delaware Application January 11, 1940, Serial No. 313,432

12 Claims.

This invention relates to a timer for an internal combustion hammer, and more particularly for a hammer of the free piston type.

One feature of this invention is that it provides improved timing means'for the ignition circuit of an internal combustion percussive hammer; another feature of this invention is that it provides more rapid change of relationship of ignition points than has heretofore been possible in hammers of the free piston type; still another feature is that the improvement enables use of a break ignition system, with attendant battery saving and other advantages; other features and advantages of this invention will be apparent from the following specification and the drawings, in which:

Fig. l'is a fragmentary vertical view, principally in section, of 'a hammer embodying this invention; Fig. 2is a detail view, principally in section, of the timer; and Fig. 3 is a sectional view of the device shown in Fig. 2, transverse to such view.

Internal combustion percussive hammers, particularly of the free piston type, present a number of peculiar problems. One of the important ones is the generation and proper control of the timing of an ignition spark, since such a hammer has no rotating cam shaft or similar conventional parts.

The hammer here partially illustrated is of the free piston type, of the same general shape and operation as the hammers disclosed in Saunders Patent 1,813,513 and Mould Patent 1,997,071. The general operation of such a hammer is on the principle of a two-cycle internal combustion engine, a piston-hammer being freely reciprocable in the cylinder forming the body of the hammer. Means is provided for supplying a combustible charge above the piston, and when this is ignited the piston is driven downwardly to deliver an impact to the tool; then spring means return the piston to the upper part of the cylinder, whereupon' t'he cycle is repeated. The general operationof such hammers is now well known to the art, described in a number of issued patents, including those above-named, and will not be further set out here.

In order todevelop a motion which was in accordance with that of thereciprocation of the piston, so that it could be used to drive ignition timing means and keep such timing properly coordinated with the movementsof the free piston, Saunders in his above-mentioned patent inserted a plunger through the wall of his cylinder and had it contact a cam surface on the piston itself.

In this way reciprocation of the piston effected reciprocation of the plunger, the movement of the plunger always bearing a predetermined known relationship to that of the piston; and

the movement of the plunger could then be used to control and time an ignition circuit. Later developments included the provision of a rolleron the end of the plunger contacting the piston cam surface, as shown in Mould Patent 1,868,754.

Heretofore, however, it has been found impracticable to use an ignition circuit of the break type now commonly used on internal combustion engines. In a circuit of the break type the .ignition points remain closed (so that there is a constant flow of current through the primary of the ignition coil) until the spark is desired, whereupon separation of the points causes collapse of the magnetic field and creation of a high voltage in the secondary of the spark coil which develops the desired sparkacross the terminals of the plug. This is to be contrasted with ignition circuits of the make type, now employed on such hammers, where the primary circuit is normally open and the ignition points are closed when the spark is desired; in this system the circuit is provided with a separate buzzer or interrupter to make and break the circuit several times while the ignition points are closed.

In order to secure effective ignition by a system of the break type it is necessary that the ignition points separate'relatively rapidly, since slow separation results in burning of the points and in slow collapse of the field, with resultant decrease in secondary voltage. On the other hand, the practical conditions of hammers of the free piston type are-such that very sharply inclined cam surfaces cannot be used on the piston,

and this has heretofore prevented the use of a break ignition circuit. The present invention solves this and other difficulties, however, by driving the plunger relatively slowly in a conventional manner, and connecting the movable point tothe plunger through snap acting means. which eifects a relatively rapid movement of the point at the desired time interval.

In the particular embodiment. of the invention illustrated herewith the cylinder if! of the hammer has freely reciprocable therein a piston it having a cam surface 12 onione side thereof; Charge-forming means, including a. gas tank 13, supply a combustible mixture of fuel and air to the. sub-pistonspace, where it isv partially compressed. onv the downward. stroke of the pise ton and then delivered to the combustion chamber thereabove; here it is finally compressed on the upward stroke of the piston and ignited at the proper time by a spark across the terminals of the spark plug I4. The resultant expansion of the burning gases drives the piston downw-ardly to strike the anvil I5, through which the blow is delivered in conventional manner to a tool. At the end of the downward stroke the burned gases discharge through the exhaust opening 16 and the springs l1 and I8 return the piston to the top of the cylinder to repeat the cycle.

The timing apparatus comprises a housing l9 attached to the cylinder wall by any convenient means, as the studs 20, closed at its outer end by a removable cap or plate 2! attached to the remainder of the housing, as by the bolts 22. A sleeve portion provides means in which the plunger 23 is slideably journalled for reciprocatory movement, a roller 24 on the inner end of the plunger being adapted to contact the cam surface I 2 on the piston to drive the said plunger in accordance with piston reciprocation. A spring 25 urges the plunger inwardly against the cam surface to maintain proper contact with the roller.

The cap 2| carries a pair of inwardly projecting fingers 2G and 27, which fingers abut a ring 28 at the inner end to hold the ring in the position illustrated, the ring forming the stop means or shoulder for the outer end of the spring 25. The shoulder 29 at the inner end of the spring is, of course, integral with the plunger 23.

The outer end of the plunger 23 is reduced in size, as may be best seen in Figure 2, leaving space between it and the fingers 26 and 21 for members 30 and 3| forming the two sides of a link connecting the plunger and the arm 32 which is bifurcated at its upper end into hammer portions 32 and 32' In the upper part of the housing is a rod-like member 45 on which is slidably mounted a sleeve 46. The sleeve has annular shoulders 41 and 48 at its ends; is biased or urged to the right (speaking with respect to Figures 1 and 3) by a spring 49; and at one end carries the movable point 33 of the pair of cooperating contact points 33 and 34.

These points control an ignition circuit of the conventional break type found on the usual internal combustion engine, as an automobile engine; the spark being developed across the terminals of the plug I4 upon breaking or separation of the points 33 and 34.

The arm 32 is a bifurcated or U-shaped member pivotally mounted at its lower end on the pin 35 carried in the housing [9. In a bore or partial cylinder between the sides of the arm 32 a block I or rod-member 36 is slideably mounted, this block being urged away from the pivoted lower end of the arm by a spring 37. A pin 38 connects the two upper ends of the sides 30 and 3| of the link, and pivotally connects it to the slideable block 36; and the pin 39 connects the two lower ends of the sides of the link to form a pivotal connection with the end of the plunger 23. The engagement of the pin 38 with the semicylindrical bearing surface on the upper face of the block 36 serves to orient it in its slideable mounting. The members 3|] and 3| are provided with openings 40 straddling the pivot pin 35, so that there is never any contact with this pin.

The cam surface l2 on the piston l l is relatively gradually inclined, as may be seen in Figure 1. The movement of the plunger 23 as a result of the reciprocation of the piston, therefore, is a relatively sloW in and out movement. The connecting linkage between the plunger and the movable point 33, however, is such that when the roller 24 approaches the upper end of the cam surface the arm 32, which has theretofore remained in the position shown in Figure 3 with the points closed, suddenly snaps to the left. When the hammer portions 32 and 32 strike the shoulder 41 the impact moves the sleeve 46 suddenly to the left, effecting quick, sharp breaking of the circuit through the points 33 and 34.

While the plunger moves outwardly during a considerable distance of its travel along the piston, as for example one inch, the points remain closed until the piston has gotten to about oneeighth of an inch from where the spark is desired, whereupon the last slight outward movement of the plunger causes a sudden snapping apart of the points, with the attendant desired spark to explode the charge above the piston. That is, the arrangement is such that when the parts are in the position shown in Figure 3, with the points closed, the points do not change their position during outward movement of the plunger until the pin 39 has gotten to the outside of the line passing through the centers of the pins 35 and 38; but as soon as this happens the spring 31 effects a relatively rapid movement of the hammer elements which in turn, upon striking the shoulder 41 on the sleeve, effect rapid separation of the points. The points then remain open until the plunger has again moved inwardly sufficiently to cause the center of the pin 39 to lie to the inside of the line passing through the centers of the other two pins.

The improvement here disclosed enables a relatively slow or gradually inclined cam surface to be used on the" piston, with its attendant advantages in the way of lack of pounding of the roller, increased wear of the parts, and the like; yet provides extremely rapid separation of the ignition points, at the desired instant of piston reciprocation, enabling an ignition system of the break type to be used. It should be noted, moreover, that while the points separate rapidly the desirable slower closing of the circuit is secured by reason of the fact that the sleeve 46 starts to move to the right under the influence of the spring 49 as soon as the hammer portions leave the shoulder 41 and before they engage the shoulder '48. In fact, the points are closed before the hammer parts engage shoulder 48. Timing of the instant of opening and closing of the points is readily controlled by manually setting the position of the fixed point 34, and by placing shims between the housing I9 and the cylinder.

While I have shown and described certain embodiments of my invention, it is to be understood that it is capable of many modifications. Changes, therefore, in the construction and arrangement may be made without departing from the spirit and scope of the invention as disclosed in the appended claims.

I claim:

1. Timing apparatus for the ignition system of an internal combustion percussive hammer having'a piston reciprocable therein, means for supplying a combustible charge thereto, and a spark plug, including: a pair of cooperating ignition points having operative connections for controlling ignition current to effect a spark at said plug, one of said points being movable;

movable means actuated during reciprocation of said piston in said hammer; and means connecting said first mentioned means and said movable point, said means including snap-action means.

2. Timing apparatus for the ignition system of an internal combustion percussive hammer having a piston reciprocable therein, means for supplying a combustible charge thereto, and a spark plug, including: a pair of cooperating ignition points] having operative connections for controlling ignition current to effect a spark at said plug, one of said points being movable; means moved relatively slowly during reciprocation of said piston in said hammer; and means connecting said first mentioned means and said movable point, so constructed and arranged that said relatively slow movement effects relatively rapid movement of said movable point at desired intervals- 3. Timing apparatus for the ignition system of an internal combustion percussive hammer having a piston reciprocable therein, means for supplying a combustible charge thereto, and a spark plug, including: a pair of cooperating ignition points having operative connections for controlling ignition current to effect a spark at said plug, one of said points being movable; means reciprocably driven by contact with said piston; and snap-action means connecting said first mentioned means and said movable point.

4. Apparatus of the character claimed in claim 3, wherein said first mentioned means contacts a relatively gradually inclined cam surface on said piston.

5.'Timing apparatus for the ignition system of an internal combustion percussive hammer having a piston with a relatively gradually inclined cam surface thereon reciprocable in a cylinder, means for supplying a combustible charge thereto, and a spark plug, including: a pair of cooperating ignition points having operative connections for controlling ignition current to effect a spark at said plug, one of said points being movable; a plunger reciprocably mounted in the wall of said cylinder and contacting said cam surface to be driven thereby; and means connecting said plunger and movable point and including a spring, so constructed and arranged that relatively slow movement of said plunger effects relatively rapid movement of said movable point at desired intervals.

6. Timing apparatus for the ignition system of an internal combustion percussive hammer having a piston with a relatively gradually inclined cam surface thereon reciprocable in a cylinder, means for supplying a combustible charge thereto, and a spark plug, including: a pairof cooperating ignition points having operative connections for controlling ignition current to effect a spark at said plug, one of said points being movable; a plunger reciprocably mounted in the wall of said cylinder and contacting said cam surface to be driven thereby; a pivoted arm adapted to effect movement of said movable point; and means connecting said plunger and said arm and including a spring,

whereby relatively slow movement of said plunger effects relatively rapid movement of said arm at desired intervals.

7. Apparatus of the character claimed in claim 6, wherein said arm is pivoted between said plunger and the end adapted to eflect movement of said point and said connecting means is operatively connected to said arm between said end and pivot.

8. Apparatus of the character claimed in claim 6, wherein said arm is pivoted between said plunger and the end adapted to effect movement of said point and said connecting means comprises a link pivotally connected at one end to said plunger and slidably connected to said arm at the other end.

9. Timing apparatus for the ignition system of an internal combustion percussive hammer having a piston reciprocable therein, means for supplying a combustible charge thereto, and a spark plug, including: a pair of cooperating ignition points having operative connections for controlling ignition current to effect a spark at said plug; movable means carrying one of said points, said means having a shoulder thereon; and means movable in accordance with the reciprocation of said piston and adapted to strike of an internal combustion percussive hammer having a piston reciprocable therein, means for supplying a combustible charge thereto, and a spark plug, including: a pair of cooperating ignition points having operative connections for controlling ignition current to effect a spark at said plug; movable means carrying one of said points, said means having a shoulder thereon; and snap-action means, driven by contact with the piston, adapted to strike said shoulder at intervals to efiect rapid separation of the points.

11. Timing apparatus for the ignition system of an internal combustion percussive hammer having a piston with a relatively gradually inclined cam surface thereon reciprocable in a cylinder, means for supplying a combustible charge thereto, and a spark plug, including: a pair of cooperating ignition points having operative connections for controlling ignition current to effect a spark at said plug; movable means carrying one of said points, said means having a shoulder thereon; a plunger reciprocably mounted in the Wall of said cylinder and contacting said cam surface to be driven thereby; and means connecting said plunger and movable point so constructed and arranged as to deliver a blow to said shoulder at a predetermined point in the reciprocation of the piston to effect rapid separation of the points.

12. Timing apparatus for the ignition system of an internal combustion percussive hammer having a piston with a relatively gradually inclined cam surface thereon reciprocable in a cylinder, means for supplying a combustible charge thereto, and a spark plug, including: a pair of cooperating ignition points having operative connections for controlling ignition current to efiect a spark at said plug; a slidable member carrying one of said points, said member having a shoulder thereon; a pivoted arm having a portion adapted to strike said shoulder; and means connecting said plunger and said arm and including a spring, whereby relatively slow movement of said plunger effects relatively rapid movement of said arm at desired intervals.

CARL L. CHARLES. 

